1. Field of the Invention
The present invention relates to an ink jet printer for display device fabrication, and more particularly, to an apparatus and a method of driving an ink jet printer for manufacturing a, display device.
2. Description of the Background Art
Recently, in accordance with the developments and wide spread of information processing systems, importance of a display device as a visual information transfer means rises. Specifically, a cathode ray tube (CRT) has a big size, a high operational voltage, and such a technical difficulty as display distortion and the like, thereby failing to meet the recent tendency toward wide size and flatness of screen. Hence, many efforts are made to develop various flat display devices having a matrix structure each.
A plasma display panel (hereinafter abbreviated PDP) as a flat display device displays pictorial images including characters and graphics in a manner of exciting phosphor to emit light by ultraviolet rays generated from discharge of inert gas such as He+Xe and Ne+Xe. The PDP facilitates to enable a wide-screen and has such a feature as high display quality and fast response speed. And, the PDP enables its thin and slim-size implementations, thereby coming into the spotlight to be used for a wall-hanging display device.
In fabricating the PDP, printing or other photography processes are generally used in coating phosphor or electrodes. Yet, these processes are expensive as well as put limitation on resolution.
In order to overcome such limitation, to reduce costs, and to enhance high precision, some manufacturers intend to use ink jet printing. A device for driving an ink jet printer for display device fabrication according to a related art, as shown in FIG. 1, is explained as follows.
FIG. 1 is a configurational block diagram of a device for driving an ink jet printer for display device fabrication according to a related art. Referring to FIG. 1, a device for driving an ink jet printer for display device fabrication according to a related art consists of a DC/DC converter 40 outputting a prescribed drive voltage Vh, a timing controller 10 outputting a timing control signal by receiving a prescribed signal IN inputted from outside, a head driver 20 outputting a drive pulse by receiving the timing control signal outputted from the timing controller 10 and the prescribed drive voltage Vh, and an array resistor 30 receiving the drive pulse outputted from the head driver 20 to output a signal (head drive voltage) having a voltage at a prescribed level to a head.
An operation of the above-configured device for driving the ink jet printer for display device fabrication according to a related art is explained as follows.
FIG. 2 is a diagram for explaining an operation mode and standby mode for the device for driving the ink jet printer for display device fabrication according to the related art.
Referring to FIG. 2, once the prescribed signal IN for driving the head is inputted from outside, the timing controller 10 receives the signal IN to output the timing control signal having a prescribed frequency.
The head driver 20 receives the timing control signal outputted from the timing controller 10 and the prescribed drive voltage Vh outputted from the DC/DC converter 40 and then outputs the drive pulse having the level of the drive voltage Vh. In doing so, the frequency of the drive pulse is equal to that of the timing control signal. For instance, if the drive voltage Vh is 40V and if the frequency of the timing control signal is 3 KHz, the head driver 20, as shown in (a) of FIG. 2, outputs the drive pulse of 2 KHz at 40V.
Thus, the drive pulse outputted from the head driver 20 is inputted to the array resistor 30. The drive pulse is then converted according to a resistance of the array resistor 30 and a condenser value of the head connected to the array resistor 30 to be inputted to each head. In doing so, a frequency and voltage of the head drive voltage applied to the head are also equal to those of the drive pulse, respectively.
Once the head drive voltage is applied to the head, ink is jetted from a nozzle, which is a sort of hole for jetting the ink, constructing the head to print a pattern of phosphor, electrode, or the like.
On the other hand, if the ink jet printer fails to operate or is in standby mode, i.e., if the external input signal IN fails to be inputted, any kind of voltage, as shown in (b) of FIG. 2, is not applied to the head since there exists no drive pulse signal outputted from the head driver 20.
When the head drive voltage fails to be applied to the head, the ink fails to circulate to precipitate so that the nozzle may be blocked or a state of the nozzle can be changed. In case that the nozzle is blocked in the course of jetting the ink, a missing channel may be brought about.
In order to solve the above-mentioned problems, the related art method of driving the ink jet printer intends to prevent the blocked nozzle and the missing channel in a manner of applying a priming pulse having a frequency different from that of the drive pulse in the standby mode, i.e., a pulse enabling to circulate the ink instead of jetting the ink. Yet, in the related art method, since the frequency of the drive pulse on printing is different from the frequency of the priming pulse after the printing, the condition for circulating the ink is varied to affect the ink jet. Hence, the ink blocking or missing channel may take place.
Moreover, the DC/DC converter 40 of the related art device for driving the ink jet printer for display device fabrication keeps outputting the prescribed drive voltage Vh regardless of a presence or non-presence of the connection to the head. Hence, if the head is not connected, a bad influence may be put on the system.
Meanwhile, even if the same drive voltage is applied to the head driver 20, there exists a difference of voltage substantially applied to the head due to the resistance difference according to the characteristics or use of each head.
Thus, once the difference of the voltage applied to each head takes place, the voltage difference varies a jetting speed of the ink jetted from the head to differentiate an ink jet amount according to each head. Hence, brightness reduction of the panel and the difference in uniformity take place after pattern printing, which is shown in FIG. 3.
FIG. 3 is a diagram of a pattern according to a signal applied to each head of the related art device for driving the ink jet printer for display device fabrication.
Referring to FIG. 3, in applying the same drive voltage Vh to the head driver, if the voltages applied to head-1, head-2, and head-3 are 40V, 45V, and 35V, respectively due to the resistance difference between the respective heads, a pattern by the head-2 is thickest and a pattern by the head-3 is thin. Hence, the uniformity difference occurs.
Meanwhile, as mentioned in the above explanation, even if the same drive voltage is applied to the head driver 20, the ink amount jetted from the nozzle may vary due to the different features of a plurality of piezos configuring the respective heads, respectively instead of the difference between the voltages substantially applied to the heads, respectively.
FIG. 4 is a diagram of a waveform applied to a piezo configuring each head of the related art device for driving the ink jet printer for display device fabrication. Referring to FIG. 4, in case that there are thirty-two piezos configuring a head, slopes of drive waveforms or voltages applied to the channels (piezos) differ from each other, whereby an amount of ink jetted from a nozzle varies.
In case that the ink jet amount varies, the missing channel occurs to degrade the pattern uniformity.